Cleaned out float valve. Everything looks spotless. Float valve is not adjustable. Works as you would expect blowing through the inlet pipe and moving the float up and down.
Thought we had victory when starting it up and putting the warmers on - took 4 minutes to happen the first time, then happened inconsistently every 30 seconds to 2 minutes. Not sure if any improvement - seems about the same. Tried to induce it by varying the load by plugging in/unplugging warmers. Couldn't induce it. Also only does it when warm.
Troubleshot the idea that the float was low ie fuel starvation - there is definitely no cloggages in the tank, filter, pipe etc...the flow could run a V8. I turned off the fuel tap and thought this might induce it - ie if the float level is low, turning off the fuel tap would make it happen pretty quickly and consistently, ie within 1 minute (normally it takes about 4 minutes for the carb to empty and run out of fuel). It did not do it when running out of fuel (until it actually ran out of fuel).
When it happens, it is like the spark is cut for about 4 seconds, then starts firing again just as it is about to die -
https://www.youtube.com/watch?v=SCC6iW6LktU
Just as I wrote this up, I noticed on the video that the oil light comes on just when it happens...that might be the issue - it's a bit too late to be firing up the generator in the street to test this out. I'll try it later in the week when I'm back home. It certainly would explain why it happens when it's warm also I think. I did give it an oil change a few months ago and it only started happening since that - I would think it's just an oil level, however, that would make you think it would happen when cold. If it's an oil pressure sensor, the oil may not be holding pressure when it's hot - I'll dump out whatever is in there and go from there. I can't remember what I put in for grade.
May as well post up here, so someone in the future can find this post on t'internet...